The computer industry is moving toward smaller, faster, and more compact electronic systems. Nowhere is this more true than in the field of compact portable computer systems (e.g., laptop, notebook, or sub-notebook computers).
Conventional computer systems include numerous interconnected electronic components configured to accomplish a variety of different computing tasks. These electronic components are generally mounted on circuit boards contained within an enclosure or housing that (among other things) protects the components from damage. In portable computer systems, the housing serves as a carrying case and frequently includes the keyboard. As is known, housings of such portable computer systems are smaller than most “desktop” computers.
One of the important concerns in the design of computer housings is the need for adequate cooling of the electrical components during computer operation. Conventional designs address this concern by using cooling fans, heat sinks, vents, radiative cooling, and other cooling means to reduce the inside temperature of the housing, thereby preventing the overheating of the internal electronic components. In any case, these conventional approaches are directed toward removing heat from the inside of the housing in order to adequately cool the inside of the housing. Some cooling is achieved through heating and radiative cooling of the housings. However, there is an upper limit to the amount of heat that can be transferred to such housings. In a 25° C. ambient, the UL (Underwriters Laboratory) has set a maximum external surface temperature for plastic housings at 80° C. and for metal housings the maximum external surface temperature is 60° C.
As computers become faster, operating temperatures of the electrical components tend to go up. With each new generation of computers, thermal solutions become increasingly important. This becomes especially so in portable computers which are becoming smaller and smaller, thereby confining greater amounts of heat in smaller spaces.
FIG. 1 depicts a typical portable computer 1. The depicted portable computer 1 includes a display 11 and a housing 10. In order to maintain light weight and low cost, many portable computers use plastic housings 10. Such plastic housings are relatively strong and absorb heat generated by the microprocessors and other components of the computer system during operation. However, in the continuing drive for ever thinner portable computers, stronger materials are required to give the necessary strength and resilience to the thinner computer housings. Metals can be used to provide a thinner, yet sufficiently strong, housing.
FIG. 2 is a cross-section view of a computer housing 10′. The depicted metal computer housing 10′ is constructed of, for example, titanium. Mounted inside the housing are internal electronic components. Various electronic components are shown mounted on a circuit board 21, for example, a Main Logic Board. Underlying the circuit board 21 is a sheet of electrically insulating material 22. Commonly, insulating material 22 is a thin sheet of black polyester material (i.e., Mylar®) whose primary purpose is to electrically insulate the circuit board 21 from contact with the inner surface of the metal housing 10′. During ordinary course of use, the housing 10′ can be subjected to some degree of mechanical flexing and bending. In the absence of the insulating material 22, electrical contacts or the electronic components on the circuit board 21 can come into contact with the metal housing 10′, which could possibly electrically short the system. Additionally, the insulating material 22 absorbs heat generated by the electronic components. One problem with such designs is that the insulating material 22 becomes very hot during system use. This heat is transferred from the polyester insulator 22 to the housing 10′ where the external housing surface temperature can undesirably exceed the UL heat specification. Still worse, if the housing 10′ becomes too hot, it can be uncomfortable for the user or can cause heat damage to furniture upon which the computer rests. This problem is exacerbated by the higher operating temperatures of the newer, faster computers. Furthermore, as the profile of these housings 10′ becomes even slimmer, electronic components come into closer proximity to the insulating material 22, again increasing the temperature of the housing 10′.
Therefore, there is need for a method and apparatus that reduce the external temperature of computer (or other electronic device) housings.